Companion Materials

Chapter 06

Chapter 6 Diana Deutsch

II C. The auditory continuity effect

In this demonstration of the auditory continuity effect. First a pure tone is presented, with a clear gap in the middle. Following this, a complex tone is presented. Following this, the same pure tone is presented, with the gap filled by the complex tone. The pure tone now appears continuous. This sound demonstration is posted with kind permission of Yoshitaka Nakajima. [nakajima.wav]

IV D. The effect of pitch streaming on perception of temporal relationships.

This demonstration is by Leon Van Noorden, and is similar to one originally created by Leon Van Noorden (1975). A triplet pattern of two tones (ABA triplets) is repeatedly presented, with varying pitch distance between tones A and B. When these tones are close in pitch, a clear rhythm is heard, but as the tones diverge in pitch two pitch streams, one high corresponding to tone A and one low corresponding to tone B, are heard, and the rhythmic pattern is no longer perceived. [gallop.mp3]

The scale illusion was discovered by Diana Deutsch in 1973, and first published by Deutsch (1975).This pattern consists of a major scale, with successive tones alternating from ear to ear. The scale is played through earphones simultaneously in both ascending and descending form, such that whenever a tone from the ascending scale is in the right ear, a tone from the descending scale is in the left ear; and vice versa. The sequence is played repeatedly without pause. Listeners frequently experience an illusion in which the higher tones appear to be coming from one earphone and the lower tones from the other. Righthanders tend to hear the higher tones as on the right and the lower tones as on the left, but lefthanders are more varied in how the higher and lower tones are localized. [deutsch_scale_illusion.mp3]

The glissando illusion was discovered by Diana Deutsch in 1995. The illusion should be heard through stereophonically separated loudspeakers, with one to the listener's left and the other to his right. It is produced by an oboe tone played together with a sine wave that glides up and down in pitch. The two sounds are repeatedly switched between the left and right speakers; such that when the oboe tone is in the left ear the glissando is in the right hear, and vice versa. The oboe tone is heard correctly as leaping back and forth between the speakers, however the segments of the glissando appear to be joined together seamlessly, and to move around in space in accordance with its pitch motion. [deutsch_glissando_illusion.mp3]

In the octave illusion and first published by Deutsch (1974)., two tones that are spaced an octave apart are alternated repeatedly at a rate of four per second. The identical sequence is presented over headphones to both ears simultaneously, except that when the right ear receives the high tone the left ear receives the low tone, and vice versa. This pattern is almost never heard correctly, and instead produces a number of illusions. Most people hear a single tone which switches from ear to ear, while its pitch simultaneously shifts back and forth between high and low. When the earphone positions are reversed most people hear the same thing: The tone that had appeared in the right ear still appears in the right ear, and the tone that had appeared in the left ear still appears in the left ear. Righthanders tend to hear the high tone on the right and the low tone on the left; however lefthanders are more varied in where the tones appear to be coming from. [deutsch_octave_illusion.wav]

This scale was originally created by Roger Shepard in the 1960s. It is produced by a set of complex tones whose components are separated by octaves. The amplitudes of the components are scaled by a fixed, bell-shaped spectral envelope such that those in the middle of the musical range are highest, and those at the extremes are lowest. The pitch classes of the tones are varied by shifting all components of each tone up or down in log frequency. When these tones are played moving up in semitone steps, listeners hear an eternally ascending scale. When they move down in semitone steps listeners hear an eternally descending scale instead. [shepard_circular_scale.mp3]

An eternally descending glissando produced by octave related complexes

This glissando was originally created by Jean-Claude Risset in the 1960s. It is also composed of octave-related complexes, but the pattern takes the form of a glissando instead of a scale. [risset_circular_glide.mp3]

This scale was originally created by Diana Deutsch in 2004. It is produced by a sequence of tones, with each tone comprising a full harmonic series. One begins with a bank of 12 harmonic complex tones, whose fundamental frequencies range over an octave in semitone steps. For the tone with the highest fundamental, the odd and even harmonics are equal in amplitude. For the tone a semitone lower, the amplitudes of the odd harmonics are reduced relative to the even ones, so raising the perceived height of this tone. For the tone another semitone lower, the amplitudes of the odd harmonics are reduced further, so raising the perceived height of this tone to a greater extent. One continues down the octave in this way until for the tone with the lowest fundamental, the odd-numbered harmonics no longer contribute to the tone's perceived height. The tone with the lowest fundamental is therefore heard as displaced up an octave. So when these tones are played in ascending semitone steps, listeners hear an eternally ascending scale, as in this demonstration. [deutsch_circular_scale.mp3]